Collagenous colitis: A study of the distribution of morphological abnormalities and their histological detection

In collagenous colitis, the literature is conflicting concerning where in t he colon the lesions are most likely to be present and most severe. Conflic ting data furthermore shed doubt on the sensitivity of the histological det ection of the morphological abnormalities and the threshold criteria for di agnosis. We addressed these questions in 56 patients with collagenous colit is. Two hundred ninety-one coded! biopsy specimens were analyzed according to six standardized sites from cecum to rectum. Subepithelial collagen depo sits were subjectively graded in hematoxylin and eosin (H&E) sections and q uantitatively measured in trichrome-stained sections, respectively. Semiqua ntitative grading was also done for inflammatory changes of the lamina prop ria and abnormalities of the surface and crypt epithelium. The transverse c olon yielded the largest percentage of biopsy specimens (83%) interpreted a s diagnostic of collagenous colitis, and also had the largest percentage of biopsy specimens with inflammatory changes (98%). Biopsy specimens from bo th the rectosigmoid and the right colon (ascending and cecum) were signific antly less likely to be diagnostic (P < .01). Only 66% of specimens obtaine d from the rectosigmoid were diagnostic, and 18% of these were interpreted as normal. Subepithelial collagen deposits proved to be significantly thick er in the transverse (median, 46.8 mu m; range, 12 to 212.4) and descending (median, 49.2 mu m; range, 6 to 230.4) than in the rectosigmoid (median, 3 3.6 mu m; range, 9.6 to 178.8) and right colon (median, 35.4 mu m; range, 6 to 140.4), respectively (P < .01). Almost all biopsy specimens (97%) had c ollagen deposits thicker than 10 mu m. However, the subjective interpretati on "diagnostic of collagenous colitis" proved to be most consistent with a threshold of 30 mu m. Our results indicate that biopsy specimens from at le ast as proximal as the transverse colon should be obtained to definitely ru le out collagenous colitis. Furthermore, it is evident that in a given biop sy specimen, markedly abnormal subepithelial collagen deposition had to be present for an unequivocal histological diagnosis of collagenous colitis. C opyright (C) 1999 by W.B. Saunders Company.